Digital watermarking is a technique for embedding data in electronic content, such as audio-visual content, for example. A digital watermark is intended to go unnoticed by an ordinary consumer of the electronic content, but carries information that may be used for a variety of purposes. For example, an audio watermark embedded in an audio file or the audio component of audio-visual content is inaudible to a listener, but may be used to identify the producer or distributor of the content, or may identify the point of origin of the electronic file carrying the content. In addition, in the context of television (TV) transmission, watermarks may be used by rating agencies to track and identify programming content.
Communication of information via digital watermarks typically requires use of an encoder to embed the watermark into the content before its transmission, and use of a complimentary decoder for extracting or “reading” the watermark by its intended recipient. Without such a complementary decoder, a digital watermark embedded in content cannot be read, or even detected. In addition to their many legitimate uses, however, digital watermarks may be used by a contributor of content to a TV transmission to use that transmission as a vehicle for unauthorized communications. Those unauthorized communications may be undesirable for several reasons. For example, the TV network providing the transmission that includes the content carrying the unauthorized watermark is typically the Federal Communication Commission (FCC) licensee for the transmission, and may bear liability for the embedded watermark communication despite being ignorant of its presence. Consequently, a solution is needed for enabling identification of watermarked content as such without requiring use of the complementary decoder configured to detect and read a digital watermark.